This invention relates to ceramic forming techniques and more particularly relates to an apparatus and method for forming a sealed outer ring for a ceramic honeycomb structure.
Due to the inherent fragility of ceramic honeycomb structures and to the fact that they must be driven externally in many cases, (for example, a cylindrical regenerator for a gas turbine engine must be continuously rotated through hot and cold gas streams), the need arises for an outer ring of higher strength than the honeycomb structure. Several approaches to this problem have been taken in the prior art, including for example forming the outer ring as one or more separate parts and gluing these parts to the honeycomb structure with special glues or other compositions as exemplified by U.S. Pat. No. 3,251,403 or placing stressed metal bands around the outside of the structure as exemplified by U.S. Pat. No. 3,081,822. In addition to the strength requirement, the outermost or peripheral cells of the honeycomb structure must be closed in some manner to form an effective seal while the regenerator is operating in order to prevent the leakage of gas from the desired flow path in the gas turbine engine.
While these operations have been performed separately up to the present time, it would be desirable to be able to form these rings for strength and for sealing in one unitary operation, in order to render the production process more economical and commercially feasible.